Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$65.98	9.421%	$72.196	$72.20	$72.20	$72.20
Purchase #2	$85.63	13.338%	$97.0513	$97.05	$97.05	$97.10
Purchase #3	$72.28	13.638%	$82.1375	$82.14	$82.15	$82.10
Purchase #4	$208.60	13.855%	$237.5015	$237.50	$237.50	$237.50
Purchase #5	$12.34	13.137%	$13.9611	$13.96	$13.95	$14.00
Purchase #6	$126.73	12.206%	$142.1987	$142.20	$142.20	$142.20
Purchase #7	$136.42	12.722%	$153.7754	$153.78	$153.80	$153.80
7 purchase totals =	$707.98		$798.8215	$798.83	$798.85	$798.90